Means and method for suppressing interference in radio reception



Jan. 4, 1938. H, BA BREEDLOVE 2,104,635

MEANS AND METHOD FOR SUPPHESSING INTERFERENCE IN RADO RECEPTION Filed Jan. 16, 1956 5 Sheets-Sheet l A5 le WM5/miran f ryreea/VB Jan. 4, 1938.

H. B. BREEDLOVE MEANS AND METHOD FOR SUPPRESSING INTERFERE Filed Jan. 16, 1936 VMEANS AND METHOD FOR SUPPRESSING INTERFERENCE IN RADIO RECEPTION Filed Jan. 16, 1936 5 Sheets-Sheet 5 all Jam 4, 1938. H. la4 BREEDLOVE MEANS AND METHOD FOR SUPPRESSING INTERFERENCE IN RADIO RECEPTION 5 Sheets-Sheet 4 Filed Jan. 16, 1936 Jan. 4, 1938.* H. B. BREEDLOVE 0 2,104,635

MEANS AND METHOD -FOR SUPPRESSING INTERFERENCE IN RADIO RECEPTION Filed Ja n. 16, 1956 5 Sheets-Shea?I 5 Patented Jan. 4, 1938 UNlTED STATES OFFICE MEANS AND METHOD FR, SUPPRESSING' INTERFERENCE IN RADIO RECEPTION 23 Claims.

This invention relates to means and methods for removing or suppressing interference, including static, which interferes with the reception of signalling currents transmitted at radio frequencies either over wire, air, or other non-metallic circuits. It relates to the suppression or removal of such interference in complete Wire circuits, wire and non-metallic circuits or Wireless broadcast-receiving circuits.

It primarily relates to means and methods for utilizing two or more bands of frequencies, which bands preferably are adjacent bands, but which in many, or probably most, cases must be separated by intervening frequency bands, for receiving signals at radio frequencies, the interference on one band being used to demodulate and/or cancel out interference on the other or others thereof. It will be understood that the word"demodulate as here and hereinafter used, is intended to mean the removal of intensity variations or variations in amplitude by modulating or otherwise opposing them with like, but out of phase intensity variations.

It further relates to means and methods for using two or more bands of frequencies for receiving signals at radio frequencies, one of such bands being un-used, at least locally, so far as signal carrying Waves are concerned, and being used solely to receive interference, which interference is used to demodulate the interference on the other band or bands.

In general it is directed in receiving signalling currents at radio frequency, toward the utilization of interference which may enter the receiver' in one band to demodulate the interference entering in another band or bands.

In usual transmission at radio frequency, a carrier wave of desired frequency, signal modulated in intensity, is transmitted from a sending antenna and received over the antenna of a suitable receiving apparatus, such carrier waves when received being often accompanied by static or other interference which hinders or even prevents reception.

(Cl. Z50-6) Or a first carrier wave signal modulated inversely in intensity with respect to a second carrier wave modulated in intensity by the same signal, is reinverted after it is received, and detected to substantially remove the carrier wave frequency, and the intensity output of said first wave is combined with such second wave prior to final detection of the latter, in such manner that the signal intensities of the first wave supplement those of the other, whereas interference intensities entering the receiver with said first wave are inverted by the said reinversion of the first wave and when the waves are combined demodulates the interference of the second wave. Y

Or the interference intensities of a signal vacant channel, after being detected and divorced from their carrier wave, are used to demodulate the interference of two, or even a greater plurality of, signal modulated carrier waves each of a different frequency and of a frequency different from that of the signal-vacant channel;

In a modification of the device, two carrier waves of different frequencies, jointly modulated out of phase inV intensity by a common signal, are received and their interferences severally demodulated by the interference intensities of a Vsignal-vacanty channel at a third frequency after said latter intensities have been freed from their carrier Wave frequency and after such demodulation, the two signal bearing carrier waves are reinverted and after final detection combined to oppose and cancel out remaining interference in- Y tensities.

It will be understood that while it is preferable to use a channel entirely signal-vacant, that a locally signal-vacant channel may be used.

Interference, While `not predeterminable as to phase, intensity, or variation in intensity, being inherently identical in phase and these characteristics in adjoining radio frequency bands, and` substantially identical in bands even though they Y are separated by a limited number of intervening bands, the primary object of this invention is to use the interference intensities on one frequency Y band for cancelling out the like phase and charinterference intensities in one band of radio frequencies for demodulating relatively inverted interference intensities in a second band of radio frequencies in which the signal intensities are in phase.

To provide means and methods for receiving signalling energy at radio frequencies, either over wire, the air, or other circuits, which means employs the interference intensities received in an energy vacant radio frequency channel, after they have been substantially freed from their carrier wave frequencies, to demodulate the interference received with a plurality of energy modulated carrier waves at different and differing radio frequencies.

To provide means and methods for utilizing the interference intensities in one signal vacant band, at radio frequency, for demodulating the interference in two bands of different and differing radio frequencies which in sending have been modulated out of phase in intensities by the same signal, and for combining the interference-demodulated intensities of such two bands in reinverted intensity phase, whereby to cancel out the remaining interference intensities.

To provide means and methods for receiving signalling energy at radio frequencies, either over wire, the air, or other circuits, which means employs two or more frequency bands, at least one of which bands carries a wave, signal modulated in intensity, and which means utilizes the interference intensities on another band of radio frequencies, after they have been substantially freed from their carrier wave frequencies, for demodulating the interference in the signal carrying band.

The means by which these and other objects are accomplished, and the manner of their accomplishment will readily be understood from the following specification on reference to the accompanying drawings, which show,I diagrammatic views of the general arrangement of receivers embodying my invention, and some of the various hookups that are effective therewith, all embodying the use of circuits for at least two frequency bands, and in which,

Fig. 1 shows the employment of two super heterodyne circuits using a single radio frequency tuner amplifier.

Fig. 2 shows the employment of two super heterodyne circuits using independent radio frequency tuner amplifiers.

Fig. 3 shows the employment of two super heterodyne circuits modulated by a third super heterodyne circuit.

Fig. 4 shows a modified form of receiver employing a tuner radio frequency circuit and a super heterodyne circuit.

Fig. 5 shows a modified receiver employing two super heterodyne circuits.

Fig. 6 is a detail applicable to Figs. 3 and 5, showing a specific hookup between two second detectors and the signal output device.

Fig. 7 shows a modifiedform of receiver employing a. tuned radio frequency circuit and a super heterodyne circuit.

Fig. 8 shows a specific hookup from one circuit accomplished through a grid of a tune, of a second circuit.

Fig. 9 shows a specific hookup particularly applicable to Figs. 4 and 5 showing one circuit coupled to a second circuit through a grid of such second circuit.

Fig, 10 shows two interconnected circuits particularly adapted for telephone service.

Fig. 11 shows two circuits and a specific hookup from one circuit to a plate circuit of the other circuit.

Fig. 12 shows two circuits and a specific hookup from one circuit to a screen grid of the other circuit.

Fig. 13 shows a fragmentary portion of two circuits and a hookup between one circuit and the control grid of the other circuit.

Referring now to the drawings in which the various parts are indicated by numerals, in Fig. 1; III is a broadly tuned radio frequency tuner amplifier, adapted to tune and separate out a band of frequencies wide enough to include two, or even several usual adjacent bands of frequencies. I I is a converter or first detector and I2 is a local oscillator, the energy from which is impressed on the converter in usual manner; the converted output being delivered in parallel to tuned intermediate frequency amplifiers I3, I4, each adapted to select and tune from the broad band a single band of intermediate frequencies, thus establishing a first and a second frequency channel. I5 and I6 are respectively the primary and secondary of a coupling and Il, I8 variable condensers. I9 is a diode of the heater type. 2D is a grounded resistance which is connected by a variably tapped lead ZI to the grid of a triode 22. The coil l5, condenser I8, diode I9 and resistor form a detector circuit the output of which is amplified by the triode 22. The plate circuit of the triode 22 is connected to the primary 23 of a modulation transformer in such manner that the audio frequency in the said primary will oppose like intermediate frequency intensity variations in the secondary 24 of the coil, this secondary being in the output circuit from the amplifier I3 to an intermediate frequency amplifier 25, the output of which amplifier is impressed on a detector 26. 2l' is an audio frequency amplifier and 25 a signal output device.

29 is a switch in a circuit of the second frequency channel, which switch when opened allows the first channel to be used in usual manner.

In Fig. 2, 53, 5I are radio frequency amplifier tuners, each adapted to receive and separate out a desired normal band of frequencies. 52, 53 are converters and 54, 55 local oscillators. 56 is an intermediate frequency amplifier and 5'! a detector. The output from the detector 5l is delivered through a circuit having a resistance 58 and variable tap 59, to the primary 6U of a modulation transformer, through a variable phase change device 6I, the secondary 62 of the transformer *being in the output circuit from the converter 52 to the first intermediate frequency amplifier 63. 54 is a second intermediate frequency amplifier, 65 a detector, 66 an audio frequency amplifier and 'I a signal output device. As in the preceding form of the device the detector 51 is connected to the primary of the transformer 60 in such manner that the audio frequency variations oppose like intensity variations in the secondary 52.

In Fig. 3, I Uil, IIJI are radio frequency tuner amplifiers, each adapted to receive and separate out a normal band of radio frequencies, IDZ, ID3 are converters which respectively receive these bands of frequencies andr I 04, H their respective local oscillators. |06 is a third radio frequency tuner amplier adapted toV receive and separate out a single band of frequencies. IIi'I is a converter or first detector and |08 a local oscillator. |09 is an intermediate frequency amplifier for the output of the converter |07, and IIO a detector for the output of the amplifier |69. The output of the detector passes through a circuit, which includes resistance I I and a variable tap ||2 and is connected through an adjustable tap- I3, to a phase-adjusting device comprising resistance H, one end of which is connected to a condenser ||5 and the opposite end to a coil I I6. The circuit from the phase-adjuster is completed preferably parallel through the respective primaries ||9 and |26 of two modulation transformers to opposite ends of a resistance unit H8. The adjustab-le tap I |1 of this unit being connected back to the detector. The output of the detectors III] is connected to the primaries H9, |26 in such manner that the current variations from this detector oppose like intensity variations in the secondaries |22 and |23. The secondary 22| of the rst of these transformers is connected in the output circuit from the converter |63, and the secondary |22 of the other transformer in the output circuit of the converter |02. The output circuit from the converter |92 leads through the secondary |22 through amn pliiiers |23, |22 to a detector |25, and the output of the converter |63 through the secondary |2| and through intermediate frequency tuner amplifiers |26, |21 to a detector |28. The circuit from the detector '|25 is inversely connected in series with the detector |28. |29 is a resistor bridging the circuit and |30 a variable tap leading back to both detectors. |3| is a signal output device.

In Fig. 4, |60|6| are radio frequency tuner amplifiers each adapted to receive and separate out a single band of frequencies. |52 is a converter or rst detector which receives the output of the tuner amplier |60, and |63 a detector which receives the output of the tuner amplifier |6|. The output circuit of the detector |53 is bridged by a variable resistor |64, which is connected by a variable tap |65 to the primary |56 of a modulation transformer having a secondary |61. |68 is a local oscillator the energy from which is impressed on the converter |62, the secondary |61 being in the connecting circuit. The primary |66 and secondary |61'of the transformer are relatively so connected in their respective circuits that the energy from the detector |63 modulates the energy from the local oscillator |63 in opposing phase relation to the interference received in the converter |62. |69, |19 are intermediate frequency amplifier tuners through which the output from the converter |62 passes to a detector |1|. |12 is a signal output device.

In Fig. 5, 2|!) is a radio frequency tuner arnplier adapted to tune and separate out a band of frequencies Wide enough to include several usual bands ofk frequencies. 2|| is a radio frequency amplifier tuner adapted to receive and separate out a normal band of frequencies. 2|2, 2|3 are respectively converters or first detectors respectively receiving the output of the tuner amplifiers 2HE and 2|I. 2M and 2|5 are tuned local oscillators Whose outputs are respectively impressed on the converters 2|2 and'2i3. 2|6 is a detector receiving the output from the converter 2|3, the output of the detector being in circuit with the primary 2|1 of a modulation transformer. 2|8 is a variable tapped resistor in the circuit. 2 i3 is the secondary of the modulation transformer, this secondary being in the output circuit from the oscillator 2M to the converter 2|2. The primary 2|1 and the secondary 2 |9 of the transformer are relatively so connected in their respective circuits that the energy from the detector 2| 6 modulates the energy from the local oscillator 2| 5| in opposing phase relation to the interference received in the converter 2|2. 229, 22| are intermediate tuner amplifiers in series which receive the output of the converter 2|2. The output of the amplifier 22| passes in parallel to intermediate'frequency ampliiiers 222, 223, which tuner amplifiers each separate out from the broad band of frequencies delivered by the amplifier 22|, a normal band of frequencies.

The outputs of the amplifiers 222-223 pass respectively to detectors 224-225, and the detected outputs are combined in opposed phase relation. 226 is a resistor bridging the circuit employed and 221 a variable tap leading back to the other leg of the circuit. 228 and 229 are respectively condensers and 236 a signal output device.

In Fig. 6; 266-26I are detectors Which are inversely connected together by legs 262--263 through a signal output device 234. 265 is a resistor bridging these legs of the circuit and 261 a variable tap leading back to a second leg of the circuit connecting the detector. 268, 269 are condensers in the legs 262, 293. The leg 262 of the circuit from the detector 266 includes a tap 212 adjustably connected to a resistor 21| of a phase adjusting circuit, the opposite ends of the resistor being respectively connected through a condenser 212, and a coil 213, and a joint lead 212 tieing the opposite ends of the condenser and coil legs together. Similar phase change devices 6| and are shown in Figs. 2 and 3, and may also be introduced in any of the other circuits shown.

in Fig. 7; 3m, 3|| are radio frequency tuner amplifiers each adapted to tune in a normal band of radio frequencies. 3|2 is a converter or first detector receiving the output of the amplifier Slo, Vand 3|3 a detector for the amplifier 3H. The output of the detector 3|3 is delivered to the primaryV 3M of a modulation transformer the secondary SEE of the transformer being in one leg of the output circuit from the amplifier 3|() to the converter 3|2. The output circuit of the detector is bridged by a resistor 3|6 having a Variabie'tap 3|? adjustably controlling the output to the primary 3M. 3|8 is a tuned local oscillator connected to the converter 3|2'. 3|9 are tuned intermediate frequency amplier stages; 322 a detector and 32| signal output device.

In Fig. 8; 366, 36| are Variable oondensers and 352 an intermediate frequency transformer, which are connected to the control rid 363 of a triple grid electron discharge device 364. 365, 356 are variable oon-densers and 361 an intermediate frequency transformer connected to the plate circuit 36S of the tube 36d. 359 and 312 are respectively the primary `and secondary of a modulation transformer, the primary 359 of this transformer being coupled to a source of modulation such as the detector 51, Fig. 2, or I l, Fig. 3. The secondary 316 of the transformer is conn nected to the suppressor grid 31| of the tube 36@ and to a desired source of suppressor grid energy. This connection through the transformer 359, 316 is such that the energy from the source of modulation is at degrees to the like intensities impressed through the circuit connection to the control grid 363.

In. Fig. 9 a variable condenser M0, a resistance fili, a transformer secondary H2 and primary M3, a condenser die?, and a triple grid tube M5, with their interconnecting circuits to the control grid M6 and the plate l||1 constitute a tuned oscillator. dit is the secondary of a modulation transformer and 4|9 the primary, one end of the secondary 416 of the transformer being connected to the suppressor grid 426 of the tube 4|5, and the opposite end to a desired source of suppressor grid energy. The primary 4| 9 of this modulation transformer is coupled to a source of modulation such as detector |63 of Fig. 4, or the detector 2|6 of Fig. 5.

In Fig. 10; 45D, 415 generally designate two telephone stations connected by a two wire, or metallic circuit, 45|. In each station are the usual plurality of signal transmitting and a corresponding number of signal receiving devices, all at radio frequency, connected in parallel to these wire circuits, and in each a similar receiving device here used as a signal-vacant device for delnodulating all of the signal receiving devices of the station.

In station 456, 452, A, B, C, D and E diagrammatically indicate the usual radio frequency transmitters and 453 their microphones, five of each being shown. 454 F, G, H, I and J are radio frequency tuner-amplifier receivers, the outputs of which amplifiers are severally passed to related detectors 455, and thence to their receiving sets 451 is a similar radio frequency tunerarnplier and 458 the detector therefor. The output of the detector 458 is passed through a phase change device 455 and a joint circuit 466, in parallel to the primaries 46| of modulation transformers, the seconda-ries 452 of these transformers being severally in the output circuit from the tuner-amplifiers 454 F, G, I-I, I, J to their respective detectors 455. 'Ihe circuit through each primary 46| is completed through a resistance 463 and adjustable tap 464. In station 410 there is an identical set-up; 412 F, G, H, I and J designating the corresponding transmitters, 414 A, B, C, D and E the radio frequency tuner amplifiers; 415 the detectors, and 416 the receiving sets; 411 the modulating tuner-amplifier and 413 the detector; these, the remaining apparatus and hookups being identical in both stations.

In Fig. 11, 5| D is a radio frequency tuner ampli- Iier coupled in usual manner through a transformer 5|| and a circuit bridged by the variable condenser 5|2 to the control grid 5|3 of an electron discharge device 5 I4. The circuit from plate 555 of this device leads through the primary of a transformer 5|6 and through a coil 5|1 and lead 5|6 to a source of energy not shown. 5| 9 are usual radio frequency stages, 520 an usual nal detector and 52| a signal indicating device, these comprising one receiver.

525 is a similar radio frequency tuner amplier coupled in usual manner'through a transformer 526 and circuit bridged by a variable condenser 512i' to the plate circuit 528 of a diode detector 529. The cathode 53|! of the diode is connected to ground through a resistance 53|. 532 is a variable tap connected through a phase change device 533 to the control grid 534 of an amplifier tube 535. The plate circuit 536 of this tube is connected to the lead 5|8 from an energy source, and through primary of transformer 5|6 to plate 5|5 of the tube 5|4.

In Fig. l2, 5561's a radio frequency tuner amplifier, coupled in usual manner through a transformer 55| and circuit bridged by a variable condenser 552 to the control grid 553 of an electron discharge device 554. Plate 555 of this device is connected through the primary of a transformer and a lead 551 to a source of energy not shown. The screen grid 558 of the electron discharge device 554 is connected through a resistor 559 in a lead 560 to a source of energy not shown. 56| are usual radio frequency stages, coupled in usual manner, 562 is a nal detector and 563 a signal indicating device.

510 is a radio frequency tuner coupled in usual manner through a transformer 51| and circuit bridged by a Variable condenser 512 to the plate 513 of a diode detector 514 which has its cathode 515 grounded through a resistor 516. A variable tap 511 connects this resistor to' the control grid 518 of an amplifier tube 519. 'The plate 580 of tube 519 is connected through a coil 58| in the lead 551 and is also connected through a condenser 582 to the screen grid 558 of tube 554.

In Fig. 13; 6|0 is a tube having its control grid 6|| coupled in usual manner through a radio frequency transformer 6|2 to a preceding stage or stages of a receiver. 6|3 is a variable condenser. The plate 6|4 of tube 6|0 is connected through the primary of a transformer 6|5 and a lead 6|6 to a suitable source of energy not shown. The transformer 6|5 is connected to following stages. 625 is a diode detector of a second receiver, the diode having its plate 626 connected through the secondary of a transformer 621, and through a resistor 628 back to the cathode 629. Primary of transformer 621 is connected to a preceding stage or stages of the second receiver. 630iis a variable condenser. A

lead 63| taken from a point on the resistor 628 is connected to a lead 632 from a source of automatic volume control. A variable tap 635 from the resistor 628 is connected to the secondary of the transformer 6|2 forming part of the secondary circuit. Automatic volume control lead 632 is connected through parallel leads 633, 634 to preceding stages of both receivers, and receivs energy from a source not shown, originating from the rst receiver.

It will be understood that in any of the forms shown a disconnecting switch such as the switch 29 of Fig. 1 may be used.

It will also be understood that while superheterodyne circuits have largely been shown, radio frequency circuits may be used, except in the forms shown in Figs. 4 and 5.

In using the apparatus shown in Fig. 1 the tuner amplifier |0 is tuned to separate out a group of radio frequency bands one of which is the channel of a carrier wave bringing in the intensity modulations of a desired program or signal, and the other a channel which is either signal-vacant or brings in a diiferent carrier wave modulated inversely or out of phase in intensities by the same program or signal. 'I'hese two channels are adjacent, if conditions permit, but if not the group of bands includes intervening channels. All the channels so included in the group whether used or signal-vacant at times bring in interference or static intensities, which inherently are relatively: in phase with each other. 'Ihis group of bands so separated out is passed to the converter or first detector and is there mixed in usual manner with the energy from a local tuned oscillator |2. The output of the converter is led over two circuits to the intermediate frequency tuner-amplifiers |3 and I4, the amplifier I3 being tuned to separate out from the group of bands that band of frequencies which contain the desired program or signal intensities and such interference intensities as accompany it. The other tuner amplier I4 is tuned to separate out from the group the other desired band of frequencies, which is either signal-vacant or inversely modulated in intensity, together with its accompanying interference intensities, these intensities being in phase with the interference intensities of the other band. Should no interference or static be present the switch 20 may be opened and the first mentioned channel used. in usual manner entirely independent of the present invention.

The output of the tuner amplifier I4 passes through the coupling |5-|6, to the plate circuit of the detector diode i and through the variablel resistance 20-2l to the grid of the amplifier triode 22. The plate output of the triode 22 consisting of intensities substantially freed by the detector from the carrier wave frequency on which they entered, is impressed on the primary 23 of the modulation transformer whichhas its secondary 24 in the output circuit of the tuner amplifier I3. The interference intensities of the detected output thus impressed on the transformer demodulate and remove the interference intensities of the output from the tuner amplifier |3 with which they are out of phase and cancel them out, whereasthe reinvertedrsignal intensities being thus restored into phase, sup- -plement the signal intensities of the tuner-amplifier 3 output. Should the ouput of the tunerampliiier I4 contain no signal intensities, the signal-intensities of the tuner amplifier |3-pass unopposed, the interference intensities only acting. The output of the amplifier i3, thus freed from interference, is then in usual manner amplied in the intermediate frequency stage, detected, amplified in the audio frequency stage and delivered to the signal output device which may be the loud speaker of a radio receiver.

In using the form of device shown in Fig. 2, 'the tuner ampliers 50, 5| are respectivelyrtuned to separate out each a frequency band one of which is a channel bringing in the intensity modulations of a desired program or signal, and

the other a channel which is either signal-vacant or brings in a different carrier wave modulated inversely, or out of phase, in intensities by the same program or signal. The outputs L of these amplifiers, respectively pass to the con-k verters 52--53 in which they are mixed respectively with the respective energies from local tuned oscillators 5d and V55. The output of the converter 53 passes through the intermediate frequency tuner amplifier 56, to therdetector 51, the detected output thereof passing to the primary 60 of the modulation transformer. passing to the primary 60, the phase of the output may be advanced or retarded by shifting ,the tap of the phase-adjusting device 6|, the

`subsequent actions and results being as before outlined. Y

In using the apparatus shown in Fig. 3 the tuner amplifiers |||0| are respectively tuned to separate out each a frequency band, one of which contains a carrier wave bringing in the intensity modulations of a desired program or signal and the other a second carrier wave at a different frequency which has in sending, been modulated inversely, or out of phase, in intentuner amplifier |06. `''he interference output if any from the amplifier |06 passes to the converter |01 where it is mixed with the energy from the local oscillator |08 and passes through the tuner amplifier |09 to the detector |0. From the detector ||0 the output passes through the circuits to the primaries ||9 and |20 the output delivered to the two primaries being relatively adjusted by shifting the variable tap i|1 with reference to the resistance H8. The 'phase of the interference intensities if any, of the output from the detector ||0 are advanced or' retarded by shifting the variable tap I3 upward or downward with relation to the resistance H4 as the case may be, in order that the said interference intensities will be 180 degrees out of phase in the primaries IIS- |20 with the interference intensities in the secondaries |2|, |22 respectively and Will thereby demodulate the interference intensities in such secondaries. The interference demodulated output of the amplifier |23 passes through the amplifier |24 and the detector |25, and the interference demodulated output of the amplifier |26 through the amplifier |21 and the detector |28 and the two outputs are inversely combined in the signal output device |3| thus removing any remaining interference in the two outputs land causing the signal intensities of the two outputs to supplement one the other.

In using the form of device shown in Fig. 4 the tuner amplifiers |60|6| are respectively tuned to separate out each a frequency band, the first of which is a channel bringing in the intensity modulations of a desired program or signal and the second a channel which is either signal vacant or brings in a different carrier wave modulated inversely, or out of phase, in intensities by the same program or signal, the output lof the amplifier |60 being delivered to a converter or The output of the amplifier` V|6| is delivered to a detector |63 and passes therefirst detector |62.

from to the primary |66 of the modulation transformer, and is there used to modulate the yenergy from the oscillator |68 as it passes throughV the secondary |61 of the transformer, thus delivering from the local oscillator to the converter energy which is modulated'in interference intensities out of phase with the first channel interference intensities in the converter and provided the second carrier Wave was signal modulated, also delivering signal intensities in phase with those entering the converter in the first channel. This modulated energy from the oscillator is mixed in usual manner in the converter with the input from the radio frequency amplifier' |60, changing the radio frequency input to intermediate frequency demodulating the out of phase interference input, and either supplementing the in phase signal intensity input or having no action thereon depending on whether a signal'carrying or vacant second channel was employed.

In using the apparatus as shown in Fig. a tuner amplifier 2|0 is tuned to separate out a group of radio frequency bands including two bands carryingra desired program intensity modulated out of phase by the same signal or signals, and the output of this amplifier passed to the converter orfirst detector 2|2.

The interference intensities of a signal-vacant frequency tuner amplifier 2| the output passing to a converter or first detector 2|3 and second detector 2|6, the detectedoutput as before being used in the transformer 2|1-2l9 to modulate the energy of the local oscillator 2|4 and this' modulated energy mixed in the converter 2|2' with the output of the radio frequency amplifier 2|0 to reduce the carrier frequencies to intermediate frequencies and to demodulate the interference intensities.

The interference having been demodulated the output of the converter 2|,2 passes through the intermediate tuner ampliers 229, 22| which are broadly tuned to cover the group of frequency bands and the output therefrom is passed in parallel to the two tuner amplifiers 222, 223 which respectively separate out the two normal frequency bands desired which are still in inverted signal intensity relation. These bands then pass through the detectors 224, 225, respectively and are combined in re-inverted phase relation and delivered to the signal output device 236.

The operation of the phase change device shown in Fig. 6 is apparently obvious, Should the phase relation of the-output from the detector 266 not be exactly 180 degrees out of phase with the output of the other detector 26|, the tap 216 is shifted along the resistance 21| to vary the resistance in the circuit to the condenser and correspondingly varying the resistance to the coil, thereby varying current flow through the condenser and advancing on retarding the phase as the case may be.

Use and actions of the apparatus shown in Fig. 7 is substantially identical with that of the apparatus shownin Fig. 2, except that demodulation of the interference intensities takes place in the radio frequency stage instead of in the intermediate stages.

In using the telephone apparatus shown in Fig. 10, at station 450, the transmitters 452A-B-C- D and E are adjusted to transmit different radio frequencies, here designated A, B, C, D and E respectively, the energy of each transmitter being modulated by its respective microphone 453, or other source of signal. At station 410 the tuner-amplifier receivers 414 A, B, C, D and E are tuned respectively to thev same frequencies A, B, C, D and E, and receive, respectively, each the signal transmitted by the transmitter at like frequency in station 456.

In station 410 likewise, the transmitters 412 F, G, H, I and J are adjusted to transmit differing radio frequencies, here designated F, G, I-I, I and J, these all differing from all the frequencies A, B, C, D and E, andthe energy of each being signal modulated by its related microphone. The receivers 454 F, G, H, I and J of station 450 are respectively tuned each to receive signal modulated energy transmitted from a transmitter of corresponding frequency of station 410.

'I'he receivers 451 K and 411 Kfare tuned respectively to a frequency K not being otherwise used by either station 450 or 410 and not being signal modulated, receive only interference.

Signal-modulated energy sent out from any one of the transmitters as the transmitter 452A, and interference which has entered the circuit is received by its related receiver 414A, and the output of the receiver delivered to its detector 415. Interference likewise enters the receiver 411K, but signal intensities are rejected astheir carrier is not of the frequency K of this receiver. This interference is detected, in detector 418, and the output delivered to the primary48| ofthe modulation transformer, the secondary 482 of which transformer is connected in inverted intensity phase in the output circuit from receiver 414A and demodulates the interference intensities of such output, but having no signal modulated indr tensities has no demodulating effect on the signal intensities of the output permitting these intensities substantially interference-free to pass to the related receiver set 416.

In using the apparatus shown in Fig. 12; interference-received through radio frequency amplifier 510, is impressed on the plate 513 of detector 514, the output being impressed on tube 519 in like manner to that of Fig. 11. Plate voltage variations caused by this interference are impressed on screen grid of tube 554 through condenser 582. Interference and signal entering the radio frequency amplifier 550 is impressed on control grid of tube 554 thereby causing a variation in electronic emission corresponding to their combined energies. The screen grid 558 of this tube having energy impressed on it from other channels in an opposing phase to like interference entering on control grid, Will-create reduced sensitivity and suppress such interference, and the signal currents being unopposed pass to the secondary of the transformer 516. If two carrier waves are received having been modulated out of phase in intensity by a common signal the energy of such carrier wave as may be received through amplifier 516 will supplement the energy received through amplifier 550 by creating an increased sensitivity of tube 554 at the moment that maximum signal is impressed on its control grid 553.

In using the apparatus shown in Fig. 11; interference received in radio frequency amplifier 525 is impressed on the detector 529 through transformer 526, the detected output creating a voltage across the resistor 53|. This energy is impressed on the control grid 534 of tube 535, creating in the plate 536 energy which causes a voltage variation across primary coil of transformer |6, this voltage variation corresponding to the variation in intensity of the interference received by tube 525. The signal and interference received by radio frequency amplifier 5|0 is impressed on control grid 5|3 of tube 5|4, the plate 5|5, of whichisconnected through the primary of transformer 5|6 to the plate 536 of tube 535. The interference received on both channels is of like phase and intensity. Interference impressed at its peak intensity on the detector 529 causes maximum current to flow in said tube, and causing the voltage at plate 536 to be reduced at the same instant that the like high intensity interference is impressed on tube 5|4, thereby causing minimum voltage drop across primary coil of transformerY 5|6 and creating minimum induced current to the secondary of such transformer, the currents from this point being amplied and detected in usual manner. The signal currents having no like energy on other channel pass unopposed. If two signals are received both being intensity modulated out of phase by a common source of energy the signal received through 525 will supplement that received on 5|0 by creating maximum voltage drop across primary coil of transformer 5|6.

In using the device shown in Fig. 13, a carrier wave having desired signal intensities and possible interference, which has been separated out in preceding stages of a first receiver, is impressed on the control grid 6| of a tube in said receiver, which grid is supplied with negative energy from the source of automatic volume control through the leads 632, 63|, the resistance I628 and the variable tap 635.

The input of a second and different frequency channel either signal vacant, or having a carrier Wave modulated out of phase in intensity by the same signal as said iirst carrierwave andhaving in either case the same possible interference as the first channel, and Which has been separated out in the preceding stages of the second receiver, is impressed in usual manner on the plate 626 of detector 625, of said second receiver. Signal intensities, if any, reach the plate 626 of said second receiver substantially degrees out of phase with the signal intensities simultaneously reaching the control grid @il of said first receiver. The low intensities in said detector decrease the negative bias effect of the automatic volume control energy on the control grid of the rst receiver at the time that corresponding high intensities are being impressed on this same grid, and conversely the high intensities received in said detector increase the negative bias of said grid at the same time that corresponding low intensities are being impressed thereon, thereby supplementing the signal energies received in the rst circuit.

On the other hand interference intensities which enter the two receivers are inherently in phase when they reach 4the detector plate 626 of the second receiver, and the control grid GII of the first receiver. High intensities in the detector increase the negative bias effect of the automatic volume control energy on the control grid at the time that the like high intensities are being impressed on said control grid. And lovv intensities decrease the bias action as like low intensities reach the control grid, thus acting in both cases to cancel such intensities and their eifect on the signal intensities of the program. By shifting the position of the variable connection 6555 along the resistance G28 the percentage of effect of one receiver on the other is changed through which method equalization of inphase intensity variations is accomplished.

In the uses as set out, the mechanism employed removes, in one of the channels the entering carrier Wave frequencies, and impresses the intensities or amplitude variations brought in on s-uch Wave, free from carrier frequency, on the carrier Wave of the other channel irrespective of the frequency of the latter Wave, thus obviating necessity of frequency synchronization.

Vihat I claim is:

1. Apparatus for receiving signals at radio frequency, said apparatus including means for receiving and nally detecting the energy of tvvo differing radio frequency channels and removing the carrier frequencies thereof, and means for impressing the intensity output of the said nal detecting means of one said channel, substantially free from any carrier frequency, on the other said channel in advance of the said final detecting means thereof.

2. Apparatus for receiving signals at radio frequency, said apparatus including means for .receiving and iinally detecting the energy of a plurality of different radio frequency channels and removing the carrier frequencies thereof, and means for superposing the intensity output of the final detecting means of one said channel, substantially free from any carrier frequency, in each other of said channels, prior to said nal detection in such channel, or channels.

3. Apparatus for receiving signals at radio frequency, said apparatus including a plurality of means, each means capable. of receiving and finally detecting the energy of a different radio frequency channel, said means each including an electron discharge device, and means for impressing the output of the said detecting means of one said channel, substantially free from any carrier frequency, on a said electron discharge device, of each of the yothers of said channels, prior to their respective final detecting means.

4. Apparatus for receiving signals at radio frequency, said apparatus including a plurality of means, each said means for receiving and finally detecting the energy of a differing radio frequency channel, each said means including an electron discharge device prior to its said final detecting means; Vand means for impressing the output of one said nal detecting means substantially free from any carrier frequency on a grid of said electron discharge device of each of the other said channels.

5. Apparatus for receiving signals at radio frequency, said apparatus including at least two means, each capable of receiving and finally detecting the energy of a radio frequency channel, said means each including an electron discharge device; and means for impressing the output of one of the said final detecting means of one said channel Vsubstantially free from any carrier frequency on each other said electron discharge device, said electron discharge device being prior to the final detecting means of its said channel.

6. Apparatus for receiving signals at radio frequency, said apparatus including a plurality of means, each capable of receiving and finally detecting the energy of a different radio frequency channel, said means each including an electron discharge device, and means for impressing the detected output of a said channel substantially free from any carrier frequency on an element of a said electron discharge device of each of the other said channel or channels, said electron discharge devices being respectively located, each in its respective channel prior to the final detecting means thereof.

7. Apparatus for receiving signals at radio frequency, said apparatus including dual means each capable of receiving and finally detecting the energy of a differing radio frequency channel, said means each including an electron discharge device; and means for impressing the output of one said final detecting means on an element of said electron discharge device of the other said channel, said electron discharge device being in advance of the final detecting means of said channel. f

8. Apparatus for receivingk signals at radio frequency, said apparatus employing two frequency channels, each including a final detector, and means in said apparatus for impressing the output of one said final detector on the other of said channels in advance of the said final detector thereof With the intensities of said output inverted substantially 180 degrees in relation to their entering phase.

9. Apparatus for receiving signals at radio frequency, said apparatus employing two frequency channels, each including a tuner-amplier and a final detector; a modulation transformer having its secondary in one of said channels in advance of its said final detector, and means for impressing the output intensities of the final detector of the second of said channels cn the primary of said transformer with the intensities of said output inverted substantially 180 degrees to their entering phase or phases.

10. Apparatus for receiving signals at radio frequency, said apparatus employing three fre- CII quency channels, each including a tuner-amplier and a final detector, means for impressing the output of the final detector of the third of said channels on the first and second of said channels in advance of the said final detectors of each thereof with the intensities of said output inverted substantially 180 degrees to their entering phase er phases, and means for combining the output of said first and second channel final detectors in relatively inverted phase relation.

11. Apparatus for receiving signals at radio frequency, employing at least two frequency channels, each said channel including receiving means, final detecting means and a modulation transformer having its secondary interposed in circuit between said receiving means and said detecting means; an additional frequency channel including receiving means and final detecting means, and means for impressing the output of said last final detector in parallel on the primaries of said transformers, with the intensities of said output inverted substantially 180 degrees from their entering phase or phases.

12. Apparatus for sending and receiving signals at radio frequency, comprising two related groups of apparatus each group including a plurality of transmitters each operable at a different radio frequency and a like number of receivers each adapted to receive the output of any one of said transmitters, plus an additional modulating device; said receiving apparatus each including a tuner-amplifier and a final detector in circuit, and a modulation transformer having its secondary in said circuit in advance of said final detector; said modulating device including a tuner-amplifier and a final detector; and means for impressing the output of the final detector of said modulating device in parallel on the primaries of said transformers with the intensities of said output inverted substantially 180 degrees to their entering phase or phases.

13. Apparatus for sending and receiving signals at radio frequency comprising two related groups of apparatus, each group including a plurality of transmitters each operable at a. different radio frequency each having a microphone; and a like number of receivers each adapted to receive the output of any one of said transmitters, plus an additional modulating device for jointly modulating all of said receivers; said receivers each including a tuner-amplifier, a final detector and a receiving set in circuit and each having a modulation transformer with its secondary in its said circuit in advance of its said final detector; said modulating device including a tuner-amplier and a nal detector; and means for impressing the output of the final detector of said modulating device in parallel on the primaries of said transformers with the intensities of said output inverted substantially 180 degrees to their entering phase or phases.

14. Apparatus for receiving signals at radio frequency, said apparatus employing two frequency channels, each including an amplifying stage and a nal detector, and means for impressing the output of the final detector of one said channel on a tube element of said amplifying stage of the other said channel in advance of the final detector thereof.

15. Apparatus for receiving signals at radio frequency, said apparatus including means for receiving and finally detecting the energy of two differing radio frequency channels and removing the carrier frequencies thereof, means for inverting the phase of the intensity output of the said final detecting meansr of one said channel 186 degrees, and means for impressing the said inverted intensity output substantially free from any carrier frequency, on the other said channel in advance ofthe said nal detecting means thereof.

16. Apparatus for receiving signals at radio frequency, said apparatus including means for receiving and finally detecting the energy of a plurality of different radio frequency channels and removing the carrier frequencies thereof, means for inverting the phase of the intensity output of the said final detecting means of one said channel 180 degrees, and means for superposing the said inverted intensity output, substantially free from any carrier frequency, in each other of said channels, prior to said final detection in such channel or channels.

1'7. Apparatus for receiving signals at radio frequency, said apparatus employing two substantially independent frequency channels, each includingl a tuner-amplier and a final detector; a modulation transformer having its secondary in a first of said channels in advance of its said final detector, and its primary in the second of said channels, afterY the final detector of said second channel; means for impressing the output intensities of the final detector of said second channel on said transformer primary and means for rendering said second channel inoperative.

18. Apparatus for receiving signals at radio frequency, said apparatus employing two substantially independent frequency channels, each including a tuner-amplifier and a final detector; amodulation transformer having its secondary in a first of said channelv in advance of its final detector, and its primary in the second of said channels after the final detector of said second channel; means for impressing the output intensities of the final detector of said second channel on said transformer primary with the intensities of said output inverted substantially 180 degrees from their entering phase, or phases, and means for rendering said second channel inoperative.

19. Apparatus for receiving signals at radio frequency, said apparatus employing two frequency channels, each including an amplifying stage and a final detector, means for inverting the phase of the intensity output of one said nal detector substantially 180 degrees from its entering phase, and means for impressing said inverted intensity output on a tube element of said amplifying stage of the other said channel in advance of the final detector thereof.

20. Apparatus for receiving signals at radio frequency, said apparatus employing two frequency channels, each including a tuner-amplifier and a final detector; a modulation transformer having its secondary in one of said channels in advance of its said final detector, and means for impressing the output intensities of the final detector of the second of said channels on the primary of4 said transformer.

21. Apparatus for receiving signals at radio frequency, employing a plurality f frequency channels, each said channel including receiving means, final detecting means and a modulation transformer having its secondary interposed in circuit between said receiving means and said detecting means; an additional frequency channel including receiving means and final detecting means, and means for impressing the output of said last final detector in parallel on the primaries of said transformers.

22. Apparatus for sending and receiving signals at radio frequency, comprising two related groups of apparatus, each group including a plurality of transmitters each operable at a different radio frequency, and a like number of receivers each adapted to receive the output of any one of said transmitters, plus an additional modulating device; said receiving apparatus each including a tuner-amplier and a final detector in circuit, and a modulation transformer having its secondary in said circuit in advance of said nal detector; said modulating device including a tuner-amplier and a final detector; and means for impressing the output of the final detector of said modulating device in parallel on the primaries of said'transformers.

23. Apparatus for sending and receiving signals at radio frequency, comprising two related groups of apparatus, each group including a plurality of transmitters each operable at a different radio frequency, each having a microphone; and

a like number of receivers each adapted to receive the output of any one of said transmitters, plus an additional modulating device for jointly modulating all of said receivers; said receivers each including a tuner-amplifier, a nal detector and a receiving set in circuit, and each having a modulation transformer with its secondary in its said circuit in advance of its said nal detector; said modulating device including a tuner-amplier and a final detector; and means for impressing the output of the final detector of said modulating device in parallel on the primaries of said transformers.

HARRY B. BREEDLOVE. 

